Stunted growth and reduced yield in cassava plant is as a result of a disease called

Analyze the question: We need the disease that causes stunted growth and reduced yield in cassava.

Explain the concept: Plant diseases are often named after their visible symptoms or their cause:

• Blight: rapid browning and death of leaves, stems and other tissues. Cassava bacterial blight does exist, but it mainly causes wilting, angular leaf spots and dieback.
• Leaf curl: leaves curl and distort. It is common in crops like tomato, pepper and cotton.
• Leaf spot: small necrotic spots on leaves, mostly caused by fungi.
• Mosaic: a viral disease. Cassava mosaic disease (CMD) is caused by the cassava mosaic virus and spread by whiteflies (Bemisia tabaci) or by infected cuttings.
• Smut: a fungal disease mainly of cereals such as maize, sorghum and sugarcane, producing black, powdery spore masses.

Show the solution:

1. Cassava mosaic disease causes yellow and green mottled patterns on the leaves, which become distorted and reduced in size.
2. The infected leaves photosynthesize poorly, so the plant is stunted.
3. Less food is stored in the tubers, so the yield drops sharply. This is one of the most serious cassava diseases in Nigeria and across Africa.
4. Smut affects cereals, and leaf spot and leaf curl are not the typical cassava diseases linked with stunting and low tuber yield. Blight is a possible distractor, but the classic answer for stunting and reduced yield in cassava is mosaic.

Answer: The correct option is **D.

Tip: Link crops to their classic diseases:

• Cassava → mosaic
• Maize/sorghum → smut
• Cocoa → black pod
• Tomato/pepper → leaf curl
• Groundnut → rosette

Mosaic means "mixed patches of colour", so think of cassava leaves with a patchwork of yellow and green.